<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        ul>:first-child{
            color:red;
        }
        ul:first-child li{
            color:blue;
        }
    </style>
</head>
<body>
    <ul>
        <li>
            第一个li
        </li>
        <li>
            第二个li
        </li>
        <p>这是一个段落</p>
    </ul>
</body>
</html>